Holy cow, new issue?! Car felt like it was going to blow up...

To think that I was just going to make a great long post here detailing the whole process that it took to get the car back to being awesome...

Driving home from a movie tonight (300: Rise of an Empire, awesome by the way!) the car felt great on the freeway so once it was up to temp I had a little fun on the onramps/off traffic lights and just floored it a couple times and cruised at like 60 to 70 most the way home (only about 12 miles) and just about 3 miles from home while I'm cruising at 60 in sport mode I notice my battery needle is just slightly below 12 volt. I know that's too low for normal operation but the last couple days (before the car was in the shop) it was dropping to right around 12 volt for five or ten minutes and would then jump back up to just under 14 volt or whatever it's normally at. I figured the belt was slipping or something because I had spilled a little coolant on it during the last time I went in and replaced the thermostat housing. I tried to clean it up the best I could, but you know how coolant is, it just kinda clings to stuff. It wasn't a huge amount so I wasn't TOO worried about the alternator because that thing is made to deal with a little bit of water from time to time, right? Still, I was going to try to get a good microfiber cloth and see if I could clean the pulley and belt again to see if maybe it wouldn't dip down to 12v at times. I didn't think it was a huge issue since I was doing short trips and about 70% of the time it seemed to be running at the right voltage and charging the battery.

Anyway, getting back to tonight, I look down, see it just below 12v and then POW, ALL the lights on the dash are lit, APC (I think?), check engine, etc, all of them. My climate control completely blacked out and a HUGE loud "CLUNK" and terrible jerk felt from the transmission. During this time the voltage ran all the way up to the max 16v and stayed there for about 10 seconds or so and then all the abnormal dash lights turned off and it dropped back to about 12v. My LCD showing drive, part, etc was still "back lit" to where it looked light everything was selected. My climate control was back to normal and turned on and off when I tested it. I tried shifting to standard drive (out of sport) and then over to select which gear I wanted on my own and noticed that nothing happened on the screen AND the car didn't shift into any different gear. I tested selecting N and that did work, going back into drive I could tell I still had power, but it didn't feel as much as normal. Since I still seemed to have some sort of drive, and I was only a couple miles from home now and about to get off the freeway I let the car kinda drift down to about 35 mph and through some residential streets till I got home. Two stop signs and at each time I noticed the power felt like maybe 20% of normal and while the car did get going from a stop, it felt like it was starting in 3rd or something.

Once I got home I opened the hood and everything around the alternator looked normal, belt was still running and the pulley appeared to still be turning. I shut the car off, then turned the key a little till the dash lit up and left it like that for a few seconds and then started the engine. Didn't drive anywhere but the shifting acted and looked normal again. I could get the 1,2,3 etc again and go from park to drive etc and it felt fine with no jerks. Looked around again and the belt was fine and the pulley looked like it was turning. I THINK my battery light was now on though (ironically it's the dimmest light on the dash, either partially burned out or something, but it did look lit a little bit, as much as when all the lights are tested at engine start) and I'm a bit below 12v on the battery gauge.

So.... what the heck happened?! Did I experience "limp mode" ? What caused the voltage to steadily move up to 16v (or above, it was just maxed out) for a few seconds and then drop down to what I assume is reserve off the battery? Lets not say it's the alternator because I really don't want to break it down again for the third time in two months... also, those things are like $650! If the alternator is dead, did seriously like two ounces of coolant a week ago cause it to die? Is it more conductive then water or something and short it? What the heck... why didn't the shield it KNOWING some would spill from right above it at each service... Does anyone want to trade A6 2.7T's? LOL

Could there be any other reason for the battery light now and not charging? Any fuses or anything I can check first... STILL haven't been able to afford VagCom (and seriously won't if I drop $650 on a new alternator) and currently don't have a check engine light after I turned the car off/on. (Actually, don't think I had a CEL one the big clunk happened and the voltage dropped from 16v to 11.9 or whatever)

Could I have killed anything during it's 16v period, or is the system fairly well protected? Radio worked fine the whole time, outside lights are fine, windows, climate control system was fine after that 10 seconds or so, dash seems to look fine now when the car is started...

He mentions a wire harness at the bottom of the radiator support, and the importance of securing it. Apparently if it's not secured properly, it rubs the alternator and causes some heinous electrical issues.
I'm sure someone way more knowledgeable than myself will be along soon, but I thought this might be worth checking in the meantime.

Probably a long shot, but skip to 1:00:05 in this video:2.7T Audi A6 S4 timing belt diy Edge Motors - YouTube
He mentions a wire harness at the bottom of the radiator support, and the importance of securing it. Apparently if it's not secured properly, it rubs the alternator and causes some heinous electrical issues.
I'm sure someone way more knowledgeable than myself will be along soon, but I thought this might be worth checking in the meantime.

Cheers!
-Bob

Sounds like the major electrical problem is with the wire harness for the AC because the rubbing can cause it to melt. Anyhow, I don't recall messing with any harnesses that far down on the lock carrier or what not. In fact I don't recall messing with anything around the alternator besides the belt (changed it of course when doing the first timing belt job) and the thermostat housing above it when I went back in to replace that the second time. Yes I did mark the direction of the belt and replaced it in the same direction AND made sure it was still getting the right amount of tension.

The belt wasn't making a screeching noise that usually indicates it slipping but I figured it still could be slipping just on the alternator a little bit and NOT making that sound because of how slick coolant is. Again, tried to blot it up the best I could but was kinda hoping it would cook off after some drive time or I could find a better absorbent cloth to use and dab it up. It wasn't a lot, but like I said a couple ounces with most running down to under the car and maybe a half ounce or full ounce splashing INTO the alternator housing and on the pulley.

If I do have to replace this damn thing, can it be done WITHOUT draining the cooling system for the 3rd time (and thus bleeding it YET AGAIN)? I can get a couple inches (four, maybe five?) of extra room in the service position even with that lower radiator hose attached... can this job be done without getting in service position if I'm ready to cuss a lot?

I personally don't see it as possible, but I could be wrong. I'm reading a DIY thread on 'zine right now on replacing brushes/voltage regulators yourself on the cheap, and apparently on the B5 A4 1.8t, it's a 15 minute job that doesn't require removing the alt. Here's a link if you're interested:http://www.audizine.com/forum/showth...brushes-(Valeo)

Unfortunately, the same thread mentions what a pain it is to do on a B5 S4 2.7t, which I believe would be a similar process to our C5 A6 2.7t, if not exactly the same.

The bright side? Even if you have to assume the position to remove the alt, it's likely that you can just replace the brushes/regulator once you have it out for wayyyy less than $650. And at least now you know to check your alt next time before putting it all back together after doing the TB. :P

But again, I'm fairly new to Audis, so I could be totally wrong. Best of luck to you, brother. Been reading your recent threads, and it seems like she's been giving you hell. Hope it works out for you.